Item8Appendix120220305DETNethyBridgeStationYard

CAIRNGORMS NATION­AL PARK AUTHOR­ITY Plan­ning Com­mit­tee Agenda Item 8 Appendix 1 13/12/2024

Agenda Item 8

Appendix 1

2022/0305/DET (NA-001 – 002)

Report to Scot­tish Ministers

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Plan­ning and Envir­on­ment­al Appeals Divi­sion Had­ri­an House, Cal­l­en­dar Busi­ness Park, Falkirk, FK1 1XR Scot­tish Gov­ern­ment Riaghaltas na h‑Alba gov.scot

Report to the Scot­tish Min­is­ters Town and Coun­try Plan­ning (Scot­land) Act 1997

Report by Dav­id Buylla, a report­er appoin­ted by the Scot­tish Ministers

• Case ref­er­ence: NA-001 – 002
• Site Address: Nethy Bridge Sta­tion Yard, Nethy Bridge, High­land, PH25 3EP
• Applic­a­tion by AW Laing
• Applic­a­tion for plan­ning per­mis­sion, ref. 2022/0305/DET dated 14 Septem­ber 2023
• The devel­op­ment pro­posed: erec­tion of 21 dwellings
• Date of site vis­it: 20 Decem­ber 2023
• Date of hear­ing ses­sion: 5 Feb­ru­ary 2024
• Date of this report and recom­mend­a­tion: 30 April 2024

Recom­mend­a­tion

Refuse plan­ning permission.

Back­ground

1. This pro­pos­al seeks plan­ning per­mis­sion to redevel­op the former Nethy Bridge rail­way sta­tion yard with 21 houses. The site lies with­in the set­tle­ment bound­ary at the west­ern edge of the vil­lage and extends to approx­im­ately 0.95 hec­tares. It is an unused brown­field site, hav­ing been a rail­way yard until the 1960s. It is shown in the Scot­tish Envir­on­ment Pro­tec­tion Agency’s (SEPA’s) flood maps as being at medi­um to high risk of flood­ing from the River Nethy, which lies on the oppos­ite side of Sta­tion Road to the site.

2. The applic­ant com­mis­sioned a series of invest­ig­a­tions into the site’s flood risk. Hav­ing reviewed these, SEPA objec­ted to the pro­pos­al on flood risk grounds. On 11 August 2023, the Cairngorms Nation­al Park Author­ity (CNPA) resolved to grant plan­ning per­mis­sion to the pro­pos­al. Due to the out­stand­ing objec­tion from SEPA, it was required to refer the mat­ter to Scot­tish Ministers

3. On 19 Octo­ber 2023, Scot­tish Min­is­ters issued a dir­ec­tion under sec­tion 46 of the Town and Coun­try Plan­ning (Scot­land) Act 1997 that the applic­a­tion be referred to them for determ­in­a­tion in view of the proposal’s poten­tial con­flict with nation­al policy on flooding.

4. On 5 Feb­ru­ary I con­duc­ted a vir­tu­al hear­ing ses­sion to dis­cuss the flood risk issue. This was atten­ded by the applic­ant, SEPA, the CNPA, Nethy Bridge and Vicin­ity Com­munity Coun­cil and a mem­ber of the public.

5. This report iden­ti­fies the main issues for Min­is­ters’ con­sid­er­a­tion, my con­clu­sions on those issues and my recom­mend­a­tion as to wheth­er plan­ning per­mis­sion should be granted.

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Envir­on­ment­al Impact Assessment

1. On 13 Octo­ber 2022, the CNPA issued a screen­ing opin­ion to the effect that the pro­posed devel­op­ment is not EIA devel­op­ment. Hav­ing regard to the cri­ter­ia in sched­ule 3 to the Town and Coun­try Plan­ning (Envir­on­ment­al Impact Assess­ment) (Scot­land) Reg­u­la­tions 2017, I con­cur with that opinion.

Policy con­text

1. The devel­op­ment plan for this case com­prises Nation­al Plan­ning Frame­work 4 (NPF4) and the Cairngorms Loc­al Devel­op­ment Plan 2021 (the LDP) and its asso­ci­ated sup­ple­ment­ary guidance.

2. Of par­tic­u­lar rel­ev­ance to this case are NPF4 policies 9, 16 and 22 and LDP policies 1, 3, 5 and 10

3. Oth­er rel­ev­ant policy and guid­ance doc­u­ments include:

• The Sup­ple­ment­ary Guid­ance that accom­pan­ies the LDP

The rel­ev­ant issues for Min­is­ters’ consideration

1. Hav­ing con­sidered all the evid­ence before me, my advice is that the main con­sid­er­a­tions for Min­is­ters in decid­ing this applic­a­tion are:

• The prin­ciple of development.
• Flood risk.
• Afford­able hous­ing and oth­er bene­fits of the scheme.

The main points for the applicant

• The applic­ant sub­mit­ted a hear­ing state­ment and a clos­ing submission.

• The applic­a­tion site has been approved for res­id­en­tial devel­op­ment since 2005, with a live plan­ning per­mis­sion in place for six large homes. This is equal in vul­ner­ab­il­ity terms to the pro­posed res­id­en­tial use.

• SEPA with­drew its objec­tion to that earli­er pro­pos­al due to the expans­ive flood­plain to the west, and the fact that the oppos­ite riverb­ank is approx­im­ately 1.5 metres lower.

• The applic­a­tion site did not flood in the 1966, 1990, 2009 or 2023 events and the applic­ant is con­fid­ent that this would remain the case in the future, with any flood waters con­fined to lower-lying land.

• The cur­rent plan­ning applic­a­tion was lodged over four months pri­or to the adop­tion of NPF4 and is being required to com­ply with stand­ards that did not apply at that time. In any event, the applic­ant con­siders the pro­pos­al is com­pli­ant with NPF4, par­tic­u­larly when con­sidered ​‘in the round’ – giv­en the brown­field status of the site and the oppor­tun­ity it would provide for much-needed afford­able housing.

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• THE CNPA’s sup­port for the pro­pos­al at com­mit­tee was unanimous.

The main points for the plan­ning authority

• Hous­ing devel­op­ment with­in iden­ti­fied set­tle­ment bound­ar­ies is sup­por­ted by LDP policy 1. In accord­ance with para­graph 1.4 of that policy, the pro­pos­al would provide mod­est two and three bed­room homes to meet loc­al com­munity needs. At least 25% would be afford­able hous­ing units as is expec­ted by para­graph 1.5 of that policy.

• The author­ity has no con­cerns with the design of the pro­pos­al, which it is sat­is­fied would meet the expect­a­tions of LDP policies 1 and 3. Amen­ity stand­ards for exist­ing and future res­id­ents would also sat­is­fy the require­ments of policy 3.

• Sub­ject to a suit­able land­scap­ing scheme being com­pleted and man­aged in the long term, the author­ity is con­tent that the pro­pos­al would sat­is­fy the require­ments of LDP policies 3 and 5.

• The River Nethy, which forms part of the River Spey SAC is adja­cent to the site. The Aber­nethy Forest SPA and Craigmore Wood SPA are also nearby. How­ever, sub­ject to appro­pri­ate mit­ig­a­tion meas­ures being secured by plan­ning con­di­tions, there would be no threat to the integ­rity of these des­ig­nated sites. Some on-site biod­iversity enhance­ment could be expec­ted from the pro­posed land­scap­ing and SuDS pond. Over­all, the author­ity is con­tent that the pro­pos­al com­plies with the terms of policies 1, 3 and 4 of NPF 4 and policy 4 of the LDP.

• The author­ity is sat­is­fied that the applicant’s flood risk mod­el­ling demon­strates that the site is not at risk of flood­ing and there­fore com­plies with LDP policy 10 and NPF4 policy 22.

• The author­ity is also sat­is­fied that any mat­ters that remain unre­solved can be con­trolled or man­aged by plan­ning conditions.

The main points for Nethy Bridge and Vicin­ity Com­munity Council

• The com­munity coun­cil sub­mit­ted a clos­ing submission.

• The lack of afford­able hous­ing in the vil­lage is crit­ic­al. Many homes are bought as second or retire­ment homes at prices loc­al people can­not afford. As a res­ult, loc­al busi­nesses are strug­gling to find staff to fill vacancies.

• The applic­a­tion site is brown­field. It is ideally loc­ated for vil­lage ser­vices and the bus route.

• The site has not flooded in liv­ing memory includ­ing with­in the memory of a 96 year old res­id­ent who died recently. If SEPA’s flood maps were cor­rect it would have been flooded on a reg­u­lar basis. And many oth­er prop­er­ties (which lie at a lower level than the site) would also have been flooded. This has simply not occurred.

The main points for SEPA

• SEPA sub­mit­ted a hear­ing state­ment and a clos­ing submission.

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• The site lies with­in the func­tion­al flood­plain as iden­ti­fied in SEPA’s Flood Maps and is at medi­um to high risk of flood­ing from the River Nethy.

• NPF4 requires devel­op­ment to avoid areas at risk of flood­ing in a 1 in 200 year plus cli­mate change event.

• Dif­fer­ent meth­ods can legit­im­ately be used to carry out flood risk cal­cu­la­tions for an ungauged catch­ment such as the River Nethy. How­ever, a pre­cau­tion­ary approach must always be applied, as the cal­cu­lated prob­ab­il­ity of flood­ing is always a best estim­ate rather than a pre­cise forecast.

• The applicant’s flood risk assess­ment work presents a range of poten­tial flood­ing scen­ari­os, depend­ing on which meth­od is used to cal­cu­late flow. This work demon­strates the sig­ni­fic­ant dif­fer­ence in pre­dicted flood extent that arises with rel­at­ively minor changes in flow. This emphas­ises the import­ance of not assum­ing the low­est pre­dicted flow.

• His­tor­ic flood­ing events in the loc­al­ity also con­firm the need to adopt a pre­cau­tion­ary approach.

• SEPA is not sat­is­fied that con­di­tion 12 in Appendix 1 to this report, which was agreed between the applic­ant and coun­cil, would ensure that the devel­op­ment avoided flood risk. In SEPA’s view, such an approach would res­ult in people and new prop­erty being put at risk of flood­ing, poten­tially with no means of escape, and could also (due to the pro­posed land rais­ing) res­ult in increased flood risk for exist­ing loc­al properties.

Oth­er parties’ cases

1. Mr James Fraser, a res­id­ent of the vil­lage is strongly in sup­port of the pro­pos­al due to the severe short­age of afford­able hous­ing in the vil­lage. His fam­ily has lived in the vil­lage for many years and has nev­er seen the site flooded.

Reporter’s find­ings The prin­ciple of development

1. The site is not alloc­ated for devel­op­ment but is situ­ated with­in the LDP-defined set­tle­ment bound­ary of Nethy Bridge, As such, the prin­ciple of res­id­en­tial devel­op­ment is sup­por­ted by LDP policy 1.

2. NPF4 policy 16 f) only sup­ports hous­ing devel­op­ment on unal­loc­ated sites in lim­ited cir­cum­stances. It first requires all pro­pos­als to be sup­por­ted by an agreed times­cale for build-out. The applic­ant has indic­ated its inten­tion to devel­op the site over the short to medi­um term in order to address the press­ing need it has iden­ti­fied (which the CNPA and com­munity coun­cil appear to endorse) for smal­ler, lower-cost homes. In the cir­cum­stances, I am sat­is­fied that this policy require­ment is met.

3. Policy 16 f) then requires the pro­pos­al to be con­sist­ent with the plan spa­tial strategy and oth­er rel­ev­ant policies includ­ing loc­al liv­ing and 20 minute neigh­bour­hoods. No party has raised con­cerns with this issue. The site is situ­ated with­in a lar­ger vil­lage, which has a range of ser­vices and a bus route with­in a reas­on­able walk­ing dis­tance. There­fore, set­ting aside the ques­tion of flood risk, I find the pro­pos­al to meet this expect­a­tion. For similar

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reas­ons, I am sat­is­fied that it would meet the NPF4 policy 15 require­ment to con­trib­ute to loc­al liv­ing and 20 minute neighbourhoods.

1. The final rel­ev­ant require­ment of policy 16 f) is that the pro­pos­al rep­res­ents a ​“smal­ler scale” oppor­tun­ity with­in an exist­ing set­tle­ment bound­ary. ​“Smal­ler scale” is not defined, but I am sat­is­fied that, in the con­text of Nethy Bridge, this pro­pos­al can reas­on­ably be described as such.

2. As a brown­field site, the prin­ciple of redevel­op­ment can also draw sup­port from NPF4 policy 9.

3. Tak­ing all factors (oth­er than flood risk, which I dis­cuss below) into account, I find this site to be accept­able in prin­ciple for the pro­posed res­id­en­tial development.

Flood risk

1. Policy 22 (a) of NPF4 only sup­ports devel­op­ment pro­pos­als on land that is ​“at risk of flood­ing or in a flood risk area” where one of four cir­cum­stances (set out in parts a) i to a) iv)) applies. That term is defined in the gloss­ary to NPF4 as land which has an annu­al prob­ab­il­ity of being flooded of great­er than 0.5% (in oth­er words, in a 1 in 200 year return peri­od event), which must include an appro­pri­ate allow­ance for cli­mate change. The parties agree that the need to account for cli­mate change when defin­ing the flood risk area did not fea­ture in Scot­tish Plan­ning Policy (SPP), the pre­de­cessor to NPF4.

2. I agree with the parties that parts a) i and a) ii of the policy (which refer to essen­tial infra­struc­ture and water-com­pat­ible uses) are inap­plic­able to this proposal.

3. Refer­ring to the extant plan­ning per­mis­sion on the applic­a­tion site for a vis­it­or centre (includ­ing craft work­shops, retail and cafet­er­ia) and six large houses, the applic­ant argues that the pro­posed devel­op­ment of 21 smal­ler homes should be sup­por­ted under part a) iii of the policy (redevel­op­ment of an exist­ing build­ing or site for an equal or less vul­ner­able use).

4. Res­id­en­tial dwell­ings are iden­ti­fied in SEPA’s vul­ner­ab­il­ity guid­ance as ​“highly vul­ner­able”. How­ever, SEPA rejects the applicant’s pro­pos­i­tion that the exist­ence of highly vul­ner­able uses with­in the extant per­mis­sion for the applic­a­tion site would enable the pro­pos­al to bene­fit from policy 22 part a) iii.

5. Its prin­cip­al argu­ment is that the extant per­mis­sion has not been imple­men­ted, so the exist­ing use of the site is open land, which is a less sens­it­ive use than that pro­posed. It also con­tends that, even if it were cor­rect to have regard to the res­id­en­tial ele­ment of the extant redevel­op­ment per­mis­sion, the num­ber of highly vul­ner­able recept­ors would increase sig­ni­fic­antly as a con­sequence of this pro­pos­al, so the pro­pos­al should be con­sidered more vul­ner­able than the con­sen­ted scheme.

6. I agree with SEPA that the start­ing point needs to be a com­par­is­on between the cur­rent land use (an appar­ently unused site) and that, which is now pro­posed. The extant per­mis­sion was gran­ted before the adop­tion of both ele­ments of the cur­rent devel­op­ment plan, in accord­ance with which, the cur­rent pro­pos­al must (unless mater­i­al con­sid­er­a­tions indic­ate oth­er­wise) be determ­ined. The exist­ence of an extant plan­ning per­mis­sion for an altern­at­ive scheme is a mater­i­al con­sid­er­a­tion, but due to the date of that per­mis­sion and the sig­ni­fic­ance of the flood risk issue, it is not one to which I con­sider sig­ni­fic­ant weight should be giv­en. And even if it were to be giv­en sig­ni­fic­ant weight, I agree with SEPA that, if this site were found to be ​“at risk of flood­ing or in a flood risk area”, then the proposed

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sig­ni­fic­ant increase in homes (and there­fore res­id­ents) when com­pared with the extant per­mis­sion, would pre­vent the pro­pos­al being sup­por­ted by policy 22 a) iii.

1. Part a) iv of NPF4 policy 22 poten­tially sup­ports the redevel­op­ment of pre­vi­ously developed land (which the applic­a­tion site is – hav­ing been the sta­tion yard until the 1960s). How­ever, I agree with SEPA that not all pre­vi­ously developed land qual­i­fies for such sup­port. It is stip­u­lated “..where the LDP has iden­ti­fied a need to bring these into pos­it­ive use and where pro­pos­als demon­strate that long-term safety and resi­li­ence can be secured in accord­ance with rel­ev­ant SEPA advice.”

2. SEPA’s view, with which I con­cur, is that policy 22 a) iv would allow a plan­ning author­ity to alloc­ate a pre­vi­ously developed site in an LDP where it con­sidered that redevel­op­ment was of such import­ance that it should be per­mit­ted, des­pite the iden­ti­fied flood risk and where, pri­or to alloc­a­tion, it had worked with SEPA to ensure that the bene­fits it could deliv­er would be secured in a way that would min­im­ise risk to future site occu­pi­ers and neigh­bours. SEPA states that the inten­tion was to allow such alloc­ated sites to pro­ceed as an excep­tion to the avoid­ance prin­ciple that is the con­firmed first prin­ciple of NPF4 with regard to flood risk, so that devel­op­ment on key regen­er­a­tion sites could be raised on stilts above flood levels so as to allow flood risk to be man­aged on site.

3. The applic­ant points out that its site is elev­ated above nat­ur­al sur­round­ing ground level, but I do not regard that as a rel­ev­ant con­sid­er­a­tion to an assess­ment of the pro­pos­al against this part of the policy. The key ques­tion is not wheth­er the site is elev­ated but wheth­er the LDP has iden­ti­fied a need to bring it into pos­it­ive use, which the parties agree it has not. There is also likely to be a mater­i­al dif­fer­ence in terms of its inter­ac­tion with flood­wa­ter, between a stil­ted devel­op­ment, where flood water could pass under build­ings rel­at­ively unim­peded and one where the ground level of the entire site was raised above its surroundings.

4. Tak­ing all mat­ters into account, I con­clude that part a) iv of the policy does not apply.

5. There­fore I find that none of the cir­cum­stances where policy 22 offers sup­port to devel­op­ment pro­pos­als on land that is ​“at risk of flood­ing or in a flood risk area” are rel­ev­ant to this pro­pos­al. As such, if the site falls with­in that descrip­tion, its devel­op­ment in the man­ner that is pro­posed would be con­trary to that policy.

6. LDP policy 10.2 takes a sim­il­ar approach to NPF4. Among oth­er things, it requires all devel­op­ment to be ​“free from Medi­um to High risk of flood­ing from all sources”. And, in com­mon with NPF4, when car­ry­ing out such an assess­ment, it requires the pre­dicted impacts of cli­mate change to be taken into account.

7. In excep­tion­al cases, where devel­op­ment is per­mit­ted in a Medi­um to High flood risk area, policy 10.2 states that water resi­li­ent mater­i­als and con­struc­tion may be required. As such excep­tion­al cases are not defined, I sought the parties’ views on what they might be.

8. The applic­ant sug­ges­ted a devel­op­ment for a less or equally vul­ner­able use than the exist­ing might qual­i­fy. The CNPA believes it would depend on it being demon­strated that vul­ner­ab­il­ity would be reduced as a con­sequence of appro­pri­ate mit­ig­a­tion meas­ures that were accept­able to its flood risk team and SEPA. I note that the CNPA did not indic­ate that the appeal site was being treated as an excep­tion­al case. How­ever, Mr Fraser noted that the CNPA had recently taken such an approach at a site in Aviemore.

9. SEPA, in response to Mr Fraser’s com­ments on the Aviemore site, stated that that pro­pos­al involved mov­ing to a less vul­ner­able use. It also poin­ted out that extens­ive work

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was under­taken with SEPA to ensure that the pro­pos­al would not lead to an increase in flood risk else­where. There­fore, if that is an example of where an excep­tion to the nor­mal require­ments of Policy 10.2 can be made, it is not com­par­able to the cir­cum­stances of the appeal pro­pos­al – where vul­ner­ab­il­ity is increas­ing and SEPA has con­cerns over the effect of devel­op­ing this site on neigh­bour­ing occu­pi­ers’ flood risk.

1. Tak­ing all of the sub­mis­sions into account, I am not per­suaded that it has been demon­strated that this pro­pos­al should be regarded as an ​“excep­tion­al case” under LDP policy 10.2. And even if it had been, as there is no such excep­tion in NPF4 policy 22, which post-dates the LDP, it is quite pos­sible that this pro­vi­sion of policy 10.2 would be found to be incom­pat­ible with policy 22 and there­fore super­seded by it.

2. Tak­ing all factors into account, I con­clude that, if the applic­a­tion site is found not to be ​“free from Medi­um to High risk of flood­ing from all sources” then the pro­pos­al would be con­trary to LDP policy 10.2.

3. In light of the above policy con­clu­sions, the key con­sid­er­a­tion when assess­ing wheth­er, in respect of flood risk, the pro­pos­al is in accord­ance with the devel­op­ment plan, is the level of such risk that can reas­on­ably be assigned to the applic­a­tion site.

4. The applic­ant acknow­ledges that the site lies with­in an area that is indic­ated in SEPA’s Future Flood Maps as being at medi­um to high risk of flood­ing. How­ever, it does not accept that this provides a real­ist­ic assess­ment of the like­li­hood that this site would flood.

5. The applic­ant also cri­ti­cises SEPA’s sep­ar­ate 10 year flood maps for indic­at­ing that prop­er­ties in Mill Lane, a short way upstream of the site should flood every ten years when, in real­ity, they have not flooded in recent memory. SEPA acknow­ledges that there are uncer­tain­ties in its flood maps, as they rely on an assump­tion that the chan­nel capa­city for all water­courses is approx­im­ately equal to the Medi­an Annu­al Max­im­um Flood (QMED), which in some cases can res­ult in over, or under, estim­a­tion of the likely flood extent. For this reas­on they are used as part of the screen­ing pro­cess when decid­ing wheth­er to request a pro­pos­al-spe­cif­ic flood risk assess­ment. They are nev­er used for decision mak­ing. And SEPA advises that the 1 in 10 years maps are affected to a much great­er degree by this issue, mean­ing they are more prone to being overly pess­im­ist­ic than the 1 in 200 year maps.

6. SEPA points out that its Future Flood Maps do not yet incor­por­ate the latest cli­mate change inform­a­tion and may there­fore under­play the full extent of risk. How­ever, it also accepts that these maps merely provide an indic­a­tion of poten­tial flood risk con­cern and con­firm­a­tion of loc­a­tions where fur­ther site-spe­cif­ic flood risk assess­ment will be required, rather than an abso­lute defin­i­tion of where devel­op­ment can and can­not take place.

7. Such fur­ther assess­ment was car­ried out by the applicant’s flood risk con­sult­ant and was veri­fied by a second con­sult­ant. SEPA is sat­is­fied with many aspects of this work includ­ing the hydraul­ic mod­el­ling. How­ever, it has con­cerns with some of the approaches and assump­tions that were made and con­cludes that it has not been demon­strated that the site is suit­able for res­id­en­tial devel­op­ment, both in terms of risk to the site’s future occu­pi­ers and also with regard to neigh­bour­ing occupiers.

8. The applicant’s ini­tial flood risk assess­ment (FRA) of March 2021 employed three dif­fer­ent Flood Estim­a­tion Hand­book (FEH) meth­ods to pre­dict river flows:

• FEH Rain­fall-Run­off (R‑R)

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• ReFH2
• WIN­FAP 4 (a stat­ist­ic­al method)

1. The FEH (R‑R) and ReFH2 meth­ods use rain­fall data to estim­ate river peak flow, where­as the WIN­FAP approach relies on the stat­ist­ic­al ana­lys­is of meas­ured flows.

2. The table below from the applicant’s FRA shows the pre­dicted peak River Nethy flows for a vari­ety of events from a 50% annu­al prob­ab­il­ity event to one with 0.5% annu­al prob­ab­il­ity. A 24% uplift was also applied to account for future cli­mate change. It should be noted that the latest SEPA guid­ance calls for a 34% uplift to reflect the most up to date under­stand­ing of poten­tial cli­mate change effects.

Table 3.1: Sum­mary of peak river flows for the vari­ous hydro­logy meth­ods for the River Nethy | Annu­al Exceedance Prob­ab­il­ity (%) | Return peri­od (years) | ReFH2 | WIN­FAP | FEH R‑R | | — | — | — | — | — | | 50 | 2 | 51.7 | 37.9 | 50.7 | | 1 | 100 | 132.2 | 83.5 | 134.7 | | 0.5 | 200 | 147.5 | 93.3 | 153.3 | | 0.5 + CC | 200 + CC | 182.9 | 115.7 | 190.1 | CC — an allow­ance for future cli­mate change

1. The applicant’s con­sult­ant opted to use the WIN­FAP (stat­ist­ic­al) approach because it believes this provides a bet­ter estim­a­tion of high flows in large catch­ments such as the River Nethy. It argues that ReFH2 and FEH R‑R are appro­pri­ate for estim­at­ing flow with­in much smal­ler catch­ments, where there is lim­ited gauging data. How­ever, they are likely to pro­duce a sig­ni­fic­ant over estim­ate for lar­ger catch­ments such as the River Nethy. The con­sult­ant advises that the rain­fall run­off meth­od­o­logy assumes a rain­fall event cov­ers the entire catch­ment area, which the applic­ant believes is unreal­ist­ic when that catch­ment is as large as the River Nethy.

2. The con­sult­ant then built a hydraul­ic mod­el of the River Nethy and asso­ci­ated flood­plain to see how this would per­form with the dif­fer­ent flow estim­ates, and car­ried out sens­it­iv­ity test­ing to see the likely effect of the Nethy Bridge, which lies just upstream of the site, being par­tially blocked. From this work it pro­duced maps of the 1 in 200 year flood­plain includ­ing an allow­ance for cli­mate change in order to determ­ine wheth­er this would affect the applic­a­tion site.

3. The con­clu­sion of this assess­ment is that the applic­a­tion site would not be with­in the 1 in 200 year (plus cli­mate change) floodplain.

4. SEPA accepts that, when estim­at­ing flow with­in a river chan­nel, dif­fer­ent approaches can legit­im­ately be employed.

5. SEPA also accepts that the size of the River Nethy catch­ment (97.8 km²) is poten­tially suited to either the rain­fall-derived or river flow tech­niques. How­ever, where flow estim­ates dif­fer sig­ni­fic­antly depend­ing on which approach is taken (as the above table con­firms they do in this instance), SEPA advises that a pre­cau­tion­ary approach must be adop­ted rather than assum­ing that the level of flow (and con­sequent risk of the river chan­nel being unable to con­tain that flow) will accord with the most optim­ist­ic forecast.

6. In this instance, the River Nethy itself is not gauged and the applicant’s WIN­FAP ana­lys­is relied on gauge data from oth­er rivers nearby. The applicant’s con­sult­ant advised that this is not unusu­al, as the major­ity of rivers in Scot­land are ungauged. It points out that an approach using stat­ist­ic­al ana­lys­is of real flow data can draw upon dec­ades of evidence

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from 1500 mon­it­or­ing sta­tions across the coun­try and can assign addi­tion­al weight to data from loc­al sta­tions. In this instance, the Rivers Dul­nain and Spey in the loc­al­ity were stud­ied, for which sev­er­al dec­ades of gauging data are available.

1. SEPA’s view is that there will be high­er uncer­tainty in estim­at­ing flows for an ungauged catch­ment such as this, than for one where gauging data is avail­able. And even in a gauged catch­ment, as 200 years of data is not avail­able, the require­ment for extra­pol­a­tion inev­it­ably reduces the degree of con­fid­ence one can have in the data. It states that a study has found that stand­ard tech­niques can sig­ni­fic­antly under­es­tim­ate the steep­ness of growth curves, mean­ing flood flows for a 1 in 200 year event for example could be sig­ni­fic­antly underestimated.

2. The applic­ant notes that the pic­ture obtained from its ana­lys­is of loc­al gauging data is con­sist­ent with the anec­dot­al evid­ence it has obtained from loc­al res­id­ents. While it accepts that neither source of data cov­ers a 200 year peri­od, this is com­pensated for by the fact that mul­tiple data sources were included with­in its stat­ist­ic­al ana­lys­is. The applic­ant accepts that the events that it stud­ied were not 1 in 200 year events. How­ever, it is con­fid­ent that it can extra­pol­ate from the stud­ied events to pre­dict the likely flow in such an event.

3. SEPA states that the guid­ance against the use of rain­fall run­off meth­ods applies to catch­ments exceed­ing 1000 km², far lar­ger than the approx­im­ately 100 km² area of the Nethy catch­ment. There­fore, ana­lyses that rely on rain­fall run­off must be con­sidered along­side any stat­ist­ic­al ana­lyses of flow data. The approach should be pre­cau­tion­ary (but not overly con­ser­vat­ive), as is expec­ted by NPF4, bear­ing in mind that no meth­od­o­logy can provide more than a best estimate.

4. The applicant’s ana­lys­is of the River Spey using the altern­at­ive meth­od­o­lo­gies was cited as evid­ence that rain­fall run­off approaches were overly pess­im­ist­ic. How­ever, SEPA does not accept that use­ful con­clu­sions can be drawn from the applicant’s find­ing that the rain­fall run­off meth­od gives unreal­ist­ic res­ults for the River Spey, as the catch­ment area of that river is over 1700 km², which sig­ni­fic­antly exceeds the max­im­um catch­ment size that is con­sidered suit­able for such meth­od­o­logy. The applicant’s response is that it serves to demon­strate that, as catch­ment size increases, the applic­ab­il­ity of the rain­fall run­off meth­od decreases.

5. My view is that, as the Spey catch­ment is over 17 times the size of the Nethy and nearly twice the size that the guid­ance advises is the max­im­um for the rain­fall run­off meth­od­o­logy, no use­ful con­clu­sions can be drawn from an applic­a­tion of that meth­od­o­logy to that catchment.

6. For the River Nethy, SEPA notes that, accord­ing to the applicant’s stat­ist­ic­al ana­lys­is of flow data from oth­er rivers, flood water would reach the edge of the site but not enter, where­as, using a rain­fall run­off mod­el, the site would flood entirely. The applicant’s ana­lys­is sug­gests that a dif­fer­ence in flow of only around 10% would determ­ine wheth­er the site was likely to be entirely flooded or to be nar­rowly avoided. Against that back­ground, SEPA con­siders it reas­on­able to take a cau­tious approach before assum­ing that the most favour­able out­come would be the most accurate.

7. SEPA also quer­ies why the applicant’s stat­ist­ic­al ana­lys­is did not use gauging data from the River Fesh­ie, giv­en its rel­at­ive prox­im­ity to the Nethy and the fact that it also drains the Cairngorms. SEPA states that this river is more hydro­lo­gic­ally sim­il­ar to the Nethy than the Dul­nain and, from its ana­lys­is of rain­fall radar, appears to exper­i­ence sim­il­ar weath­er pat­terns to the Nethy. SEPA notes from its own ana­lys­is of that catch­ment that there is a

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much closer cor­rel­a­tion in flow rates derived from the rain­fall run­off and stat­ist­ic­al ana­lys­is meth­od­o­lo­gies for the Fesh­ie, which sug­gests the applicant’s find­ing that the former approach pro­duces unre­li­ably pess­im­ist­ic res­ults for the Nethy should be treated with caution.

1. The applic­ant con­firms that it did include the Fesh­ie in its ana­lys­is. How­ever, it believes the Fesh­ie catch­ment is, in fact, less hydro­lo­gic­ally sim­il­ar to the Nethy than the Dul­nain and also has gauged data for a short­er time peri­od (around 30 years rather than approx­im­ately 70 years for the Dul­nain). It is also around 20 kilo­metres away from the site where­as the Dul­nain is approx­im­ately 5 kilo­metres away. The applic­ant notes that advice from the Envir­on­ment Agency in Eng­land is that sta­tions that are closer to a site should be giv­en high­er weighting.

2. SEPA states that hydro­lo­gic­al sim­il­ar­ity is the first factor that determ­ines wheth­er a catch­ment should be included in the pool­ing group for ana­lys­is (and main­tains its view that the Fesh­ie ranks high­er in that regard than the Dul­nain) but accepts that prox­im­ity to the site is also a consideration.

3. The River Avon has a sig­ni­fic­antly lar­ger catch­ment than the Nethy (approx­im­ately 500 km²) but is still with­in the size range where the guid­ance indic­ates a rain­fall run­off approach may be accept­able. SEPA’s ana­lys­is of this river also pro­duced sim­il­ar res­ults for the rain­fall run­off and stat­ist­ic­al ana­lys­is meth­ods. Again, SEPA believes this sug­gests the use of rain­fall run­off can­not simply be ruled out for a catch­ment such as the Nethy.

4. SEPA describes the records for the Dul­nain sta­tion as odd, as peak flow levels in dif­fer­ent events appear to be essen­tially identic­al. It pos­tu­lates that, at times of high water level, the gauging sta­tion may be bypassing or per­haps upstream fea­tures such as flood plain stor­age capa­city or the screen­ing effect of a nearby bridge might be gen­er­at­ing res­ults that are pecu­li­ar to the loc­a­tion of the Dul­nain sta­tion. Once again, it expresses con­cern that too much reli­ance should not be placed on the res­ults from this source.

5. SEPA argues that, in order to test the plaus­ib­il­ity of the estim­ates that each meth­od­o­logy pro­duces, his­tor­ic­al flood inform­a­tion can be taken into account. It notes that if one con­siders the 2009 event (one of sev­er­al that were con­sidered by the applic­ant and are dis­cussed below) it can be observed that the flows that led to river levels that were observed in that event are more con­sist­ent with the return peri­od that is derived from the rain­fall run­off meth­od than the stat­ist­ic­al approach.

6. A num­ber of his­tor­ic flood / high rain­fall events were referred to by both parties.

7. The ​“Great Floods” of 1829 were doc­u­mented in great detail at the time. While acknow­ledging that one can­not assign a return peri­od based on anec­dot­al evid­ence, SEPA believes the detailed account of that flood, which caused wide­spread dam­age across the area, provides a help­ful indic­at­or of what could hap­pen in the sort of event that NPF4 and LDP policy requires the land use plan­ning sys­tem to take into account when determ­in­ing the suit­ab­il­ity of a pro­posed devel­op­ment site.

8. SEPA acknow­ledges the applicant’s obser­va­tion that a con­trib­ut­or to the sever­ity of flood­ing in Nethy Bridge dur­ing the 1829 event was the wash­ing away of a saw­mill upstream, which became wedged in the bridge. Saw­mills are no longer found with­in the catch­ment so I agree with the applic­ant that such an event would not reoc­cur in a sim­il­arly intense event.

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1. How­ever, I also accept SEPA’s sub­mis­sion that, being a multi-arch bridge rather than one with a single large span, the bridge with­in the vil­lage remains a poten­tial source of block­age and there­fore a poten­tial con­trib­ut­or to an increased flood­ing effect. SEPA points out that, upstream of the site, there is ripari­an wood­land. Dur­ing storm con­di­tions, mater­i­al from the wood­land could be car­ried down­stream with the poten­tial to cre­ate a dam­ming effect at the bridge and con­sequent over-top­ping of the chan­nel. I note that the applicant’s sens­it­iv­ity test­ing to estim­ate the effect of bridge obstruc­tion only mod­elled a 10% obstruc­tion, which I agree with SEPA is not par­tic­u­larly conservative.

2. I also agree with SEPA that the intens­ity of the flows described in the account of the 1829 floods sug­gests a sig­ni­fic­ant degree of flood­ing could have been pos­sible even if the bridge had not become blocked. How­ever, the absence of any meas­ur­able data from that event pre­vents me from draw­ing any firm conclusions.

3. I agree with the applic­ant that the vil­lage has changed quite sig­ni­fic­antly since 1829. The con­struc­tion of new build­ings and the upgrad­ing of roads will have altered the path of any flood­wa­ter through the vil­lage. I also agree that it is sig­ni­fic­ant that the rail­way, of which the site forms a part, came to the vil­lage after the 1829 flood and was pre­sum­ably engin­eered to take account of what was then a rel­at­ively recent event. How­ever, I agree with SEPA that flood risk ana­lyses which util­ise the rain­fall run­off meth­od and show the site to be at risk of flood­ing, take this his­tor­ic­al land rais­ing into account.

4. The site already lies above the level of the adjoin­ing land and it is pro­posed to increase its level fur­ther in order to ensure fin­ished floor levels are above the 1 in 200 year plus cli­mate change level. Such factors are likely to reduce the like­li­hood of the site itself being flooded, even in an event as severe as that in 1829. How­ever, in accord­ance with NPF4 policy 22, thought must be giv­en to the poten­tial that a devel­op­ment might increase the flood risk for others.

5. There is exist­ing res­id­en­tial devel­op­ment to the imme­di­ate east (upstream) of the site, which could poten­tially be placed at great­er risk of flood­ing by the adjoin­ing down­stream land being at a high­er level. The appel­lant believes the size of the site in rela­tion to the flood­plain means ample space would remain for flood­wa­ter to flow around it, thereby avoid­ing a sig­ni­fic­ant increase in flood risk to those upstream. While I accept that there are extens­ive lower-lying fields fur­ther down­stream, the pos­sib­il­ity of this pro­pos­al caus­ing any increased risk of flood­ing of exist­ing prop­er­ties is a factor that must be taken into account.

6. Oth­er flood events in the loc­al­ity that are iden­ti­fied in SEPA’s Observed Flood Event data­base include 1799 and 1838 events, where con­tem­por­ary reports sug­gest the force of flood water in the Nethy was suf­fi­cient to des­troy bridges, and an event in 1880, which was referred to by the parties at the hear­ing ses­sion, where flood levels were recor­ded as reach­ing the girders of the rail­way bridge. For that lat­ter event, there is no evid­ence that it caused any flood­ing of the vil­lage and the applic­ant believes that, at that time, the rail­way bridge (which has since been removed) would have rep­res­en­ted the bot­tle­neck in the River Nethy. As with the 1829 event, these events provide no empir­ic­al data to assist in the determ­in­a­tion of this case. How­ever, they are illus­trat­ive of the poten­tial for the Nethy and oth­er loc­al water­courses to be affected by sig­ni­fic­ant events, the intens­ity of which may exceed any in liv­ing memory.

7. In an event in 1966, the River Spey exper­i­enced its second highest water flow in 69 years. The applic­a­tion site was in use as a coal yard at that time and a loc­al res­id­ent whose fam­ily knew the oper­at­ors of that business,